Technologies of this type are used in order to amplify electrical signals in a wide range of applications. Here, the electrical signal to be amplified is received at an amplifier input, amplified with the aid of an amplifier circuit and provided as an amplified electrical signal at the amplifier output.
Amplifier circuits can be built to be single- or multiple-stage. It is known in particular to execute amplifier stages of this type using transistors.
One possible field of application of electrical signal amplifiers is devices for receiving and/or for transmitting radio signals.
In radio receivers, the first component behind the antenna is generally a low-noise amplifier (LNA). Its task is to amplify the usually very weak received input signal in such a manner that the inherent noise of the subsequent electronics no longer constitutes significant interference. This LNA is a filigree component, designed for very low reception powers and should also consume as little power as possible itself. A radio receiver regularly receives not only the desired communication signal. If a strong transmitter is located in the vicinity thereof, the received power can therefore easily exceed the provided power level by 1000 times. A conventional LNA is destroyed in this case. Often, the transmission/reception system itself sends the strong signal, for example in the case of a radar or a radio interface of a satellite. It is then necessary to protect the LNA from too large of reception power. By default or standard, a protective circuit is therefore provided between LNA and antenna. This short-circuits a too large of a signal at the antenna as an electronic fuse. This protective circuit cannot be integrated on a chip with the LNA, however. The mounting technology becomes more expensive, the structure becomes large and heavy and the reliability suffers accordingly. A protective circuit suppresses the received signal and as a result impairs the signal-noise ratio.